In one type of micromachined device for sensing inertial motion about an angular rate axis, a suspended mass is dithered (oscillated) with a certain amplitude and frequency along a dither axis. The dither axis is orthogonal to an axis that is sensitive to acceleration, and also to the rate axis. The rotation of the suspended mass about the rate axis and its velocity along the dither axis produce a Coriolis acceleration along the sensitive axis. This acceleration is twice the cross product of the dithering velocity and the rate of rotation. The device measures this Coriolis acceleration and any linear acceleration along the sensitive axis.
In a device disclosed in U.S. Pat. No. 5,241,861 (which has a background section describing the general principles of operation of such a device), two accelerometers are disposed side-by-side and are each suspended from a frame by a pair of flexures. By using two accelerometers that are dithered in an equal and opposite manner, the linear acceleration components and rotational acceleration components can be determined by sum and difference techniques. The two accelerometers are connected with a single link that extends from a corner of one accelerometer and across a region between the accelerometers to a corner of the other accelerometer diagonally across the region. As recited in that patent, the link has a pivoting point to permit the link to pivot such that when one of the accelerometers is moved, an equal and opposite motion is imparted to the other accelerometer. The device in that patent is bulk micromachined. Such a process is expensive and the anisotropic etching that is required for precision limits the form of the linkage.